Lewis Acid Supported Nickel Nitrenoids.

ABSTRACT

Metalation of the polynucleating ligand F,tbs LH6 (1,3,5-C6 H9 (NC6 H3 -4-F-2-NSiMe2 t Bu)3 ) with two equivalents of Zn(N(SiMe3 )2 )2 affords the dinuclear product (F,tbs LH2 )Zn2 (1), which can be further deprotonated to yield (F,tbs L)Zn2 Li2 (OEt2 )4 (2). Transmetalation of 2 with NiCl2 (py)2 yields the heterometallic, trinuclear cluster (F,tbs L)Zn2 Ni(py) (3). Reduction of 3 with KC8 affords [KC222 ][(F,tbs L)Zn2 Ni] (4) which features a monovalent Ni centre. Addition of 1-adamantyl azide to 4 generates the bridging µ3 -nitrenoid adduct [K(THF)3 ][(F,tbs L)Zn2 Ni(µ3 -NAd)] (5). EPR spectroscopy reveals that the anionic cluster possesses a doublet ground state (S = 1 / 2 ${{ 1/2 }}$ ). Cyclic voltammetry of 5 reveals two fully reversible redox events. The dianionic nitrenoid [K2 (THF)9 ][(F,tbs L)Zn2 Ni(µ3 -NAd)] (6) was isolated and characterized while the neutral redox isomer was observed to undergo both intra- and intermolecular H-atom abstraction processes. Ni K-edge XAS studies suggest a divalent oxidation state for the Ni centres in both the monoanionic and dianionic [Zn2 Ni] nitrenoid complexes. However, DFT analysis suggests Ni-borne oxidation for 5.